1. Field
Example embodiments relate to a method of manufacturing a semiconductor device, and more particularly, to a method of forming an aluminum oxide layer and a method of manufacturing a charge trap memory device using the same.
2. Description of the Related Art
Because the amount of data to be securely stored for a relatively long time may be increased and a data storage device, e.g., a memory stick, for moving a task result to another place may be provided, there is a need for a non-volatile memory device wherein data may be electrically stored and erased and which may conserve stored data even when power is not supplied.
Conventionally, increased capacity non-volatile memory devices, e.g., NAND flash memory devices, may be used. The NAND flash memory device may have a structure in which a floating gate for storing charges (e.g., data) and a control gate for controlling the storing of charges in the floating gate may be sequentially laminated. However, the floating gate may include a conductive material, e.g., doped polysilicon, which may cause increased parasitic capacitance between adjacent memory cells when higher integration is desired.
Accordingly, in order to solve the aforementioned problem of the conventional NAND flash memory device, there has been research on non-volatile memory devices referred to as Metal-Oxide-Insulator-Oxide-Semiconductor (MOIOS) memory devices, e.g., Silicon-Oxide-Nitride-Oxide-Semiconductor (SONOS) memory devices or Metal-Oxide-Nitride-Oxide-Semiconductor (MONOS) memory devices. The SONOS memory device may use silicon as a material for the control gate, but the MONOS memory device may use a metal as the material for the control gate.
The MOIOS memory device may include a charge trap layer, e.g., a silicon nitride (Si3N4) film, instead of a floating gate, which includes polysilicon, in order to store charges. For example, a structure of a memory cell in the MOIOS memory device may include an oxide film, a nitride film, and an oxide film, which may be sequentially laminated between a substrate and the control gate. The MOIOS memory device may use a characteristic, whereby a threshold voltage may be shifted as charges may be trapped in the nitride film.
A dielectric constant of the silicon nitride film and a silicon-oxide film in the conventional MOIOS memory device, e.g., the SONOS memory device, may be relatively low. Thus, the conventional MOIOS memory device may have an increased operation voltage, decreased speed for recording (programming) and erasing data, and relatively short retention time (a time during which stored data may be conserved). One method to increase the retention time may be to use an aluminum oxide (Al2O3) layer, which has an alpha-phase crystalline structure, as a blocking layer.
The aluminum oxide (Al2O3) layer having the alpha-phase crystalline structure may be formed by thermal treating an amorphous aluminum oxide (Al2O3) layer at a temperature higher than about 1200° C. However, a silicon substrate may bend due to thermal stress from the thermal treatment process. Hence, the aluminum oxide (Al2O3) layer having the alpha-phase crystalline structure may be difficult to use as the blocking layer.